Varicella-zoster virus (VZV) causes chickenpox and shingles. The goals of this project are to construct VZV mutants to identify VZV genes that are important in virus growth and latency, and to test whether these mutants could serve as candidate live virus vaccines by inoculating animals with the mutants. Inactivation of the VZV glycoprotein I gene resulted in a virus that was impaired for adsorption to cells and impaired for growth in tissue culture cells. Inactivation of another VZV gene, ORF9A, reduced the ability of the virus to form fused cells (syncytia) in vitro. Inactivation of the VZV ORF66 gene showed that this gene product was important for modifying (phosphorylating) proteins. A reporter gene (beta-galactosidase) was inserted into the VZV genome and guinea pigs were inoculated intraocularly with VZV expressing the reporter gene. The animals developed a chronic eye infection (uveitis) with inflammatory cells in the eye. The reporter gene was expressed in various parts of the eye, including the retina, up to 3 months after infection.